Theoretical Study on the Rhodium-Catalyzed Electrochemical C-H Phosphorylation: Insights into the Effect of Electro-oxidation on the Reaction Mechanism

Themerging of transition-metal-catalyzed C-H bond activationwith electro-oxidation has evolved into an appealing protocol foroxidative C-H bond functionalization. Nevertheless, specificeffects of the electro-oxidation process on the reaction mechanismof transition-metal catalysis have rarely been investigated. Herein,we present a comprehensive computational study on the rhodium-catalyzedelectrochemical C-H phosphorylation of 2-phenylpyridine bydiphenylphosphine oxide to reveal the mechanistic details. The effectsof electro-oxidation on the three major chemical processes, i.e.,C-H activation, P-H activation, and reductive elimination/C-Pbond formation, were thoroughly addressed by considering the chemicalsteps at the Rh(III), Rh(IV), and Rh(V) oxidation states. The calculationsdemonstrated that the C-H activation prefers to take placeat the Rh(III) state, P-H activation at the Rh(IV) state, andreductive elimination at the Rh(V) state. Without electrochemicaloxidation, the total barrier for the reductive elimination occurringat the Rh(III) center is unsurmountable under the experimental temperature.The mechanistic insights disclosed in the present study are expectedto be beneficial in understanding the transition-metal-catalyzed electro-oxidativeC-H bond functionalization.